Unselected in the 2017 MLB draft, Kelly signed with the Oakland Athletics as an undrafted free agent for a $500 signing bonus.[3] He pitched in the rookie-level Arizona League during 2017.[4] The Athletics released Kelly in April 2018.[2] Kelly later said, "My first year I probably paid to play to be honest with you. I definitely lost money."[3]
Los Angeles Angels
Kelly signed with the Los Angeles Angels organization and played for three teams in the Angels' system, reaching the Class A-Advanced level with the Inland Empire 66ers of the California League; in 18 total relief appearances during the season, he posted a 2.93 ERA and struck out 41 batters in 43 innings pitched.[4] Kelly began the 2019 season with the Mobile BayBears of the Double-ASouthern League,[5] and also played one game with Inland Empire, accruing an overall 3–7 record in 21 games (13 starts) with a 4.88 ERA.[4] The Angels released Kelly during the COVID-19 shutdown in 2020.[3] Shortly thereafter, Kelly underwent surgery on his elbow to have a ligament reattached.[6]
Boston Red Sox
On January 4, 2021, Kelly signed a minor league contract with the Boston Red Sox organization. He spent the year playing for the Double-A Portland Sea Dogs and the Triple-AWorcester Red Sox.[3] He had a 1.69 ERA in 21 relief appearances for Portland before he was promoted to Worcester, where he had a 2.89 ERA in 15 relief appearances. In 2022, the Red Sox invited Kelly to spring training as a non-roster player and he returned to Worcester for the beginning of the season.[7] He accrued a 2.72 ERA for Worcester through August 29,[8] when he was added to Boston's major-league roster.[9] Kelly made his MLB debut that evening, against the Minnesota Twins.[10] He was on the paternity list for three days in early September.[11] In 13 relief appearances with Boston, Kelly pitched to a 1–0 record with 3.95 ERA while striking out 11 batters in 13+2⁄3 innings.[12] Kelly was the 2022 recipient of the Lou Gorman Award issued by the Red Sox organization.[13]
Kelly began the 2023 season in Boston's bullpen.[14] He was placed on the injured list on April 13 due to right elbow inflammation.[15] Three days later, he was transferred to the 60-day injured list.[16] On May 3, it was announced that Kelly would miss roughly four months after undergoing a successful ulnar nerve transposition revision in his right elbow.[17] He was activated from the injured list on September 24,[18] and successfully pitched for the Red Sox after going 166 days between major-league appearances.[19]
Kelly was optioned to Triple–A Worcester to begin the 2024 season.[20] On April 24, he was recalled from Worcester to replace injured pitcher Brayan Bello on the active roster.[21] Kelly was optioned to Triple-A again on May 26 to make room for pitcher Brad Keller, who had just signed a one-year contract with Boston.[22] Kelly was once again promoted to the major-league roster on June 5.[23] He made his first MLB start on June 9 against the Chicago White Sox, pitching two scoreless innings as an opener.[24]
Personal life
Kelly is married and resides in South Carolina in the offseason.[6] He and his wife, Brittany, had their first child in September 2022.[25]
